Reciprocating pump systems, such as sucker rod pump systems, extract fluids from a well and employ a downhole pump connected to a driving source at the surface. A rod string connects the surface driving force to the downhole pump in the well. When operated, the driving source cyclically raises and lowers the downhole pump, and with each stroke, the downhole pump lifts well fluids toward the surface.
For example, FIG. 1 shows a sucker rod pump system 10 used to produce fluid from a well. A downhole pump 14 has a barrel 16 with a standing valve 24 located at the bottom. The standing valve 24 allows fluid to enter from the wellbore, but does not allow the fluid to leave. Inside the pump barrel 16, a plunger 20 has a traveling valve 22 located at the top. The traveling valve 22 allows fluid to move from below the plunger 20 to the production tubing 18 above, but does not allow fluid to return from the tubing 18 to the pump barrel 16 below the plunger 20. A driving source (e.g., a pump jack 11) at the surface connects by a rod string 12 to the plunger 20 and moves the plunger 20 up and down cyclically in upstrokes and downstrokes.
During the upstroke, the traveling valve 22 is closed, and any fluid above the plunger 20 in the production tubing 18 is lifted towards the surface. Meanwhile, the standing valve 24 opens and allows fluid to enter the pump barrel 16 from the wellbore. At the top of stroke (TOS), the standing valve 24 closes and holds in the fluid that has entered the pump barrel 16. During the downstroke, the traveling valve 22 initially remains closed until the plunger 20 reaches the surface of the fluid in the barrel 16. Sufficient pressure builds up in the fluid below the traveling valve 22 to balance the pressure. After the pressure balances, the traveling valve 22 opens and the plunger 20 continues to move downward to its lowest position to fill the pump 14. The reciprocating process is repeated to lift fluid in the tubing.
In many applications, such as in reciprocating pump systems noted above, operators may want to inject chemicals to assist in the control of corrosion, water, scale, paraffin, salt, and Hydrogen Sulfide (H2S) in the production tubing. One way to inject chemicals uses a capillary injection system, which can deliver the chemicals downhole using a capillary string. In addition to controlling buildup and the like, the capillary injection system can be used to inject a lifting chemical to offset a reduction in bottom hole pressure (BHP) that typically occurs as a hydrocarbon reservoir is produced.
Chemical injections have been developed to mitigate or eliminate these difficulties. For example, surfactants are commonly injected into wells to de-water them. Other chemicals are used to counter the effects of emulsions and precipitates and to provide corrosion protection. If the well is untreated, it is well known that corrosive materials can rapidly degrade wellbore components, such as sucker rods. Of course, if these components must be replaced, the non-productive time for the well will result in lost or slowed production.
Spoolable tubing has been used for delivering the above mentioned chemicals. Examples of spoolable tubing are capillary tubing and coiled tubing. FIG. 2A shows a bottom hole assembly of the prior art in which chemicals are delivered with a capillary string S. Briefly, the well has casing C with perforations at a production zone. A production string T having threadably interconnected joints extends from a wellhead (not shown) at the surface to a tubing anchor 40 and a reciprocating rod pump P. The tubing anchor 40 anchors the production string T in the casing C and allows the production string T to be held in tension in the wellbore. This has a number of known advantages.
Below the tubing anchor 40, the assembly has the sucker rod pump P and may have a perforated sub (not shown). The sucker rod pump P is connected to a sucker rod string R extending through the production tubing T to the surface. As already noted, reciprocation of the string R axially reciprocates the pump P to transport fluids from the formation through the production tubing T to the surface.
To deliver chemicals downhole, the capillary string S extends from the wellhead (not shown) at the surface and along the tubing T. The capillary string S is typically banded to the production tubing T with various bands. Eventually, the capillary string S terminates at the production tubing T uphole of the tubing anchor 40, where injected chemicals are delivered.
In FIG. 2B, the production tubing T has a gas lift mandrel M with or without a valve (not shown) disposed above the tubing anchor 40. The capillary string S passes down to the gas lift mandrel M. At this point, the end of the capillary string S terminates at the mandrel M so chemicals can be injected internally into the production tubing T through the mandrel M uphole of the tubing anchor.
These traditional treatment methods in FIGS. 2A-2B simply inject chemicals uphole of the rod pump P. In general, these methods can achieve a poor ratio of how much treatment is applied compared to how much treatment is effectively delivered as needed. In FIG. 2A, chemicals are lost and do not reach the rod pump P. In FIG. 2B, the rod pump P, tubing anchor 40, and lower portion of the production tubing T are not sufficiently treated.
To improve the chemical injection, it has been proposed in the prior art to extend the end of the capillary string past the tubing anchor and closer to the inlet of the rod pump. For example, FIG. 2C illustrates a capillary injection system according to the prior art for injecting chemicals below a tubing anchor 40 near a subsurface reciprocating pump P. With this arrangement, the delivered chemicals from the capillary string S can enter the tubing string T through the rod pump R, which has a number of benefits. The primary issue then is how to pass the capillary string S past the tubing anchor 40, which is used to support the production tubing T in tension inside the casing as the reciprocating rod R operates the rod pump P.
As disclosed in U.S. Pat. No. 4,605,063, a solution has been proposed in the prior art in which a capillary string is simply passed through a conventional tubing anchor. Referring to FIG. 3, a tubing anchor 40 is connected to a production string (not shown). The anchor 40 has radially expandable slips 50, which are shown engaged with the casing C. A capillary string 30 extends from the surface to the tubing anchor 40 and can be attached to the tubing with bands (not shown). Past the anchor, the capillary string 30 extends to a subsurface position a sucker rod pump (See FIG. 2C).
The tubing anchor 40 is incorporated into the production string to prevent vertical movement of the tubing string. The tubing anchor 40 has an axially extending tubular body 41 conventionally attached to the tubing T by upper and lower threaded couplings 43a-b. The tubular body 41 has upper and lower threads 41a, 41c adjacent its upper and lower ends. The upper threads 41a are of an opposite hand from the lower threads 41c. At least one axially extending groove 41b is located along the exterior surface of the tubular body 41 and extends through both the upper and lower threads 41a and 41c. Although not shown, the groove 41b has a dovetail cross-sectional configuration.
An upper conical expander 42 has inner threads 42a engagable with the tubular body's upper threads 41a, and the expander 12 is positioned concentrically around tubular body 41 adjacent threads 41a. The expander 42 has a downwardly facing conical surface 42c. A similar lower expander 52 has an upwardly facing conical surface 52a. This lower expander 52 has internal threads 52c and is located adjacent the lower end of the tubular body 41. The internal threads 52c are nonfunctional after assembly. In a retracted position (not shown), the threads 52c are not in engagement with the body's lower threads 41c. 
The anchoring slips 50 are positioned concentrically encircling the tubular body 41 between the upper and lower expanders 42 and 52. When expanded against the casing, the anchoring slips 50 can securely engage to prevent vertical movement in either direction. The anchoring slips 50 are received within openings or windows 44a defined within an exterior tubular housing 44 encircling the expanders 42 and 52 and the tubular body 41. Coil springs 60 extend circumferentially between adjacent anchoring slips 50 and inwardly bias the anchoring slips 50 to retracted positions.
A torque pin 62 attached to the lower expander 52 extends through an axially extending slot 44b located in the outer housing 44. The torque pin 62 thus rotationally secures the outer housing 44 to the lower expander 52, and the windows 44a rotationally secure each radially expandable anchoring slip 50 to the outer housing 44. The lower expander 52 is attached to the expander sleeve 66 with shear pins 64. Sleeve 66 has threaded connections 66c on its interior engagable with the lower threads 41c located on the tubular body 41. Rotation of tubular body 41 will therefore cause movement of the expander sleeve 66 and the lower expander 52 relative thereto.
A nut assembly 46 and 48 secures the outer housing 44 to the tubular body 41. A flexible drag spring 56 is secured to the tubular housing 44 by means of conventional screws 58. The drag spring 56 is outwardly biased and engages the casing C to prevent rotation of the outer housing 44 relative to the casing C. Thus, rotation of the upper and lower expanders 42 and 52 and the anchoring slips 50 relative to the casing is resisted by drag spring 56.
To secure the tubing anchor 40 and the tubing T with respect to the casing C, the tubing T can be rotated thus imparting rotation to the tubular body 41. Rotation of tubular body 41 occurs while the upper expander 42 is rotationally restrained by the outer housing 44 and by the drag springs 56. Therefore, the threads 41a and 42a move the upper expander 42 axially relative to the anchoring slips 50. The slips 50 and the tubular housing 44 are initially moved downwardly relative to tubular body 41.
Eventually, the lower expander 52 moves downwardly into engagement with the body's lower threads 41c whereupon continued rotation of tubular body 41 causes the lower expander 52 to move in the opposite direction toward the slip 50 and the upper expander 42. Continued rotation shifts the upper and lower expanders 42, 52 toward each other and ultimately expands the anchoring slips 50 outwardly into engagement with the casing C. Eventually, sufficient rotation is imparted to the tubular body 41 to fully expand the anchoring slips 50 and to prevent further axial movement of the tubing string T in either direction.
The tubing anchor 40 can be released by sufficient upward tension on the tubing string T to shear the shear pins 64 holding the lower expander 52 fixed relative to the tubular body 41. These shear pins 64 are chosen with a sufficient strength to prevent release under normal anticipated tensile loads.
Since the anchoring slips 50 are actuated by rotational movement of the tubular body 41 and the tubing string T, it will be apparent that the capillary string 30 attached to the tubing T will interfere with the normal expansion of the slips 50 since the capillary string 30 must move rotationally with the tubing T. As shown, a separate conduit or section of the capillary string 30 is provided with upper and lower conventional attachments for attachment to upper and lower sections of the capillary string. This intermediate section of the capillary string 30 comprises a separate section of flow line of the same type and diameter as that of the remainder of the string 30. The intermediate section of the capillary string 30 is received within the body's dovetail groove 41b and extends along the exterior of the tubular body 41 through the upper and lower expanders 42 and 52 and through the encircling anchoring slips 50. This groove 41b is sufficiently deep to permit the capillary string 30 be received therein without interfering with the threaded connections 41a-42a or 41c-52c of the expanders 42, 52. In this way, a path is provided for injection of fluids through the tubing anchor 40 to a subsurface location below the tubing anchor 40, such as adjacent perforations in the casing.
The tubing anchor 40 of FIG. 3 require multiple turns for the slips 50 to be expanded outward and set. In this respect, the tubing anchor 40 is similar to a conventional threaded anchor that requires 9 to 12 rotations to set the anchor with the threads (41a and 41c) in FIG. 3. As a consequence, the tubing anchor 40 requires the anchor to be “screwed” together to activate. In use then, it may not be effectively possible to pass the capillary string 30 through the anchor 40 and rotate the tubing T and capillary string 30 multiple times to set the anchor 40 without potentially causing damage to the capillary string 30. Additionally, configuring the shear pins 62 on the expander sleeve 66 to release the anchor 40 may be less than ideal because the expander sleeve 66 has a complicated arrangement in which the sleeve 66 is engaged with the body's lower thread 41c, with the lower expander 52, with the torque pin 62, and with the outer housing 44.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.